The invention relates to ball screw integrated linear guide units preferably used while incorporated into, for example, operating arms of robots and X-Y tables. More particularly, the invention is directed to a ball screw integrated linear guide unit whose maintenance and durability are improved by achieving simultaneous lubrication for both a ball screw feed line and a linear guide feed line.
A conventional grease supplying structure for a single linear guide unit is disclosed, for example, in Japanese Utility Model Examined Publication No. 63-29940. This conventional example includes: an axially extending guide rail having ball rolling grooves on lateral sides thereof; and a slider stretched over the guide rail, the slider being U-shaped and having ball rolling grooves on both inner side surfaces thereof so as to confront the ball rolling grooves of the guide rail. A large number of balls are interposed between the confronting ball rolling grooves of the guide rail and the slider. The slider is axially movable by the rolling of the balls while guided by the guide rail. End caps are mounted on both front and rear end surfaces of the slider, respectively. Each end cap has a circulating passage for effecting endless circulation by causing the balls to return therethrough. The circulation passage includes semicircular recessed spaces formed on each end cap and semi-cylindrical return guides, each having arcuate outer circumference corresponding to the semi-circular curved surface of the recessed space. By attaching the return guide on the semi-circular recessed space orthogonally, the circulation passage becomes semi-doughnut-shaped.
As a result of such a construction, the recessed portion on the flat surface side of each semi-cylindrical return guide is used as a lubricating groove, and a lubricating hole opened from the lubricating groove toward the semi-doughnut-shaped circulation passage is formed by cutting through the side surface of the return guide. On the other hand, a grease feed groove is formed on an end surface of each end cap while communicated with the lubricating grooves of the return guide from a grease nipple mounting hole. The end caps are mounted on the end surfaces of the slider, and then the grease nipple is attached to the slider. Grease supplied from the grease nipple reaches the lubricating grooves of the return guides via the grease feed groove to lubricate the rolling balls.
However, the lubricating structure for the conventional example is designed to lubricate the balls of an independent linear guide unit. Therefore, if this lubricating structure is directly applied to a ball screw integrated linear guide unit in which a linear guide unit and a ball screw unit are integrated with each other, the balls for the linear guide can be lubricated, but the balls for the ball screw cannot be lubricated. Hence, in the case of the ball screw integrated linear guide unit, the ball screw balls cannot be lubricated by the grease supplied from the grease nipple; but the only means for greasing them is by loading grease within the ball screw nut in advance. Thus, the unit has to be disassembled periodically to replenish the lubricant.
The object of the invention is therefore to overcome the above problems by providing a ball screw integrated liner guide unit in which a lubricating structure applicable to lubricating balls in both a linear guide feed line and a ball screw feed line is arranged in a ball screw nut.